Retractile landing gear



y 1933' KQHENmcH sEN 2,116,395

, RETRACTILE LANDING GEAR Filed April 25, 1936 s" Sheets-Sheet 1 INVENTOR. Anal; [is-17170125912 .B'Y ATTORNEY May 3, 1938. K. HENRICHSEN RETRACTILE LANDING GEAR 5 sheets-sheet 2 Filed April 25, 1936.

. INVENTOR. %7112? Henrzbbsan ATTORNEY May 3, 1938. k. HENRICHSEN RETRACTILLBLA'NDING GEAR 5 Sheets-Sheet 4' Filed April '25, 1936 I INVENTOR. fiut 'rzmbbs'en v ATTORNEY 5 Sheets -sheet 5 INVENTOR.

ATTORNEY May 3, 1938. K. HENRICHSEN RETRACTILE LANDING GEAR Filed April 25, 1936 K112? fifennbbse Patented May 3,1933

RETRACTILE LANDING GEAR Kmit Henrichsen, Stratiord, Conn; assignor to United Aircraft Corporation, East Hartford, Conn., acorporation of Delaware I Application April 25, 1936, Serial No. 76,460 7 10 Claims. 01.249102) This invention relates to improvements in retractile landing gears and has particular reference to a landing gear. in which the wheel or a portion thereof is folded into an opening provided in a portion of the airplane upon which the land ing gear is mounted when the landing gear is retracted.

An object of'the inventionresidesin the provision of a, retractile landing gear wherein the 1 axis of the'wheel is rotated as the landing gear is retracted to bring the wheel into position to fit into an opening provided in the airplane structure carrying the landing gear.

A further object resides in the provision of means for projecting and retracting the landing gear and for releasably locking the landing gear ineither its projected or retracted position and for simultaneously rotating the axisof the landing gear wheel while the landing gear is being retracted.

A still further object resides in the provision of a strong-and rigid mounting for a retractable landing gear upon the underside of an airplane.

Another object resides in the provision of a retractile landing gear, which is light in weight and at thesame time so sturdily constructed that it will not ordinarily get out of order in use and which-is simple .and easy to operate. v r

Other objects and advantages will be more particularly pointed out hereinafter, or will be come apparent as the description proceeds.

In the accompanying drawings in which like reference'numerals are usedto designate similar parts throughout, there is illustrated a suitable mechanical embodiment of what is now considered to be the preferred form of the invention and a somewhat modified form thereof. The drawings, however, are for the purpose of illustration only and are not to be taken as limiting the invention, the scope of which is to be measured entirely by the scope of the appended claims.

In the drawings Fig. l is a side elevational view of a landing gear constructed according to the idea of this invention, the portions of the airplane 45 towhich the landing gear is attached being (ill schematically illustrated.

' Fig. 2 is a front elevational view of the landing gear construction illustrated in Fig. 1.

Fig. 3 is a perspective view on an enlarged scale of the outer swivel bearing member for the upper end of the landing gear strut.

Fig. 4 is a perspective view of the inner swivel bearing member for the upper end of thelanding gear strut.

Fig. 5 is a perspective view of a pin which connects the upper end of the landing gear strut to the inner swivel bearing member illustrated in Fig. 4.

Fig. 6 is a perspective view of the upper end of the landing gear strut.

Fig.7 is a vertical sectional view of the portion *of the landing gear strut to which the landing gear braces are connected.

Fig. 8 is a vertical sectional view of a portion of the landing gear strut intermediate its length. Fig. 9 is a vertical sectional view of aportion of the landing gear strut adjacent .to its lower end.

Fig. 10 is a vertical sectional view of the lower,

' end or wheel carrying portion of the landing gear strut.

Fig. 11 is a. longitudinal sectional view through the screw retracting mechanism.

Fig. 12 is a sectional view of a portion of an airplane wing showing the manner of attaching a landing gearconstructed according to the idea of this invention tothe airplane wing.

Fig. 13 is a plan view of the landing gear support illustrated in Fig. 12.

Fig. 14 is a side elevational view of the lower portion of a modified form of landing gear strut and, v

Fig. 15 is a sectional view on the line l5-l5 of Fig. 14.

Referring to. the drawings in detail, the numeral III indicates the wing of an airplane which may be of the low wing or center wing type in which the fuselage I2 is mounted upon or in the plane of the wing. When upon-the ground the airplane, comprising the wing Ill and fuselage l2 and other conventional parts, is supported upon a pair of-landing wheels, one of which is indicated at M by means of respective landing gear struts, one of which is generally indicated at 16. As the two landing gear struts are exactly similar in all respects with the exception that one is adapted for use upon theright handside of the airplane and the other is adapted. for use upon the left hand side thereof, it is believed that a detail description of only one of the two similar strut constructions is suflicient for the purpose of this disclosure. I

The strut I8 is of a telescopic oleo type having two telescopically associated relatively slidable portions 18 and 20. The smaller member l8 projects from the lower end of the larger member 20 .and is provided at its lower end with a wheel carrying spindle 2 2-upon which the landing wheel I4 is rotatably mounted. While the two members I8 and 20 are axially slidable relative to each other, in the form of theinvention illustrated in:

- the inner member is concentric therewith and rotational movement by a plurality of longitudinally disposed interengaging splines 24, particusurface of the outer member to provide for the relative telescopic movements between these two members. The member i8 is resiliently maintained in its extended position with respect to the member 20 by means of a coiled compression spring ll located within the inner member and bearing at its upper end against the upper end closure of the outer portion 20 of the strut and at its lowerend against an inturned flange 22 provided at the lower end of a-sleeve' member 34 secured within the lower portion of the. inner member II. The action of the compression spring 3|! is controlled by a hydraulic shock absorber which comprises a-tubular member 26 positioned within attached atits upper end'to the upper end closure of the outer member 20, a piston generally indicated at 22 upon the lower end of the tubular member 26 and a tapered finger valve 40 operating through the piston 28 inthe lower portion of the tubular member 26. A hydraulic seal 42 is provided between the interior of the lower end of the member 20 and the member is. The bydraulic fluid is ordinarily retained in a chamber M in the lower portion of the inner member l8, but when the landing wheel is subjected to the impact load of the landing airplane or strikes an obstruction which lifts the wheel and drives the inner member up into the outer member, a portion of this hydraulic fluid flows through the aperture between the tapered finger valve 40 and theopening in the piston 32 through which the finger valve projects and into the interior of the tubular member 30. when the spring forces the inner member ll outwardly with respect to the outermember 20, the fluid flows from the interior of the tubular member 36 back into the chamber 44. v

The spindle 22 is formed at its end opposite thewheel carrying portion with a cup-shaped bearing 46 which receives the lower end of the strut member ll. Bolts 42 passing through a radially extending flange 50 of the lower portion of themember II and screw threaded into the upper end of the bearing member I! rigidly secure the spindle upon the strut. In its lower end the cupahaped member 46 is provided with a seat 52 for the lower end of the finger valve and with an aperture closed by a screw threaded plug 54 through which the finger valve may be inserted or removed from. its operative associate in the landing gear strut.

The tapered-finger valve is provided with an axial bore I, the lower end of which is normally closed by a removable plug 51. Hydraulic fluid may be added to the strut by removing the plug I1 and connecting a fluid conduit with the lower end of the ilnger valve and forcing the fluid through the conduit and up through the bore 55. When the conduit 'is detached any excess fluid will flow out through the hollow finger valve until the level of the fluid in the reservoir 44 is even with the top of the finger valve. so that the finger J valve aifordsa simple and" effective means for Figs. '7 and 8, they are restrained against relative definitely maintaining the proper amount of hydraulic' fluid in the strut.

A towing link]. is securedin pivotal relation'to the bottom of the cup-shaped bearing 46 by means of the bolts 58 screw threaded into the lower portion of the bearing.

At its upper end the outer member 20 is provided with an outwardly extending flange 60 upon which is mounted the upper cover member 62 secured to the flange by suitable means such as the cap screws 64. The upper cover member $2 has an upward extension through which extends a pin receiving aperture 66 lined with a suitable bushing 68, the portion of the cover member adjacent the aperture being rounded to form a loop or ear around the aperture. This upper end of the outer strut member 2! is connected by means of its apertured cover member 62 and the transverse pin 10 withan inner swivel bearing member generally indicated at 12, the pin- 10 extending through the aperture 66 and bearing at its ends in apertures I4 provided in a hollow extension I6 on the inner .bearing member which extension receives the loop portion of the cover member 62 surrounding the aperture 88. It will be observed that this pin connection provides a hinged joint between the strut and the inner bearing member 12. The bearing member 12 is provided with exterior screw threads as indicated at II which mesh with similar screw threads 80 provided in the interior of the socket portion of an outer swivel bearing member generally indicated at 22.-

The member 82 is provided with a flat apertured flange 84 by means of which the member may be attached to the underside of the wing It, a tapered washer. 86 being interposed between the flange 84 and the undersurface of the wing to accommodate the outer bearing member to the contour of the wing surface.

In addition to the flange l4 and a stem portion 88,' the bearing member 82 is provided witha hollow socket portion 90 which rotatably receives the inner swivel bearing member 12. The socket portion 90, as clearly illustrated in Figs. 1 and 3, is disposed at an angle of degrees in both the X and Z planes to the perpendicular axis .of the flange 84 considered as the Y ordinate. Referring to Fig. 1 itwill be observed that the longitudinal axis of the socket 90 is so directed that the open end of the socket faces inwardly, downwardly and rearwardly with respect tothe wing it. The correspondingscrew threads 12' and 80 provide a bearing surface between the socket and the inner bearing member 12 so that the inner member may rotate freely in the'socket and will at the same time be restrained against load induced axial movement with respect to the socket.

The collar 28 rotatably mounted upon the screw threaded thickened portion 26 of the outer strut member II is provided with internal screw threads 92 which cooperate with the screw threads on the strut member to provide a rotatable bearing between the strut member and the collar. This collar 28 is provided with a pair of spaced apertured, rearwardly directed ears, or lugs, indicated at 24 and to these lugs there is pivotally connected one end of a brace member generally indicated at 96, the other end of which is pivotally connected by means of a pin 98 to the interior structure of the wing which will be presiour link members as clearly illustrated in Figs. 1 and 2. The lower link members I00 and I02 are pivotally connected to 'the' upper link members I and I" by means of a bearing pin Hi8 to entiy described. The brace member 86 comprises provide an elbow joint in .the brace member. the members I00 and I02 being provided with stops as indicated at I I0 to limit the relative movement between the respective links so that the pin I08 can move along the arc illustrated in Fig. 1 from a position in which the brace member is straight as illustrated in full lines, to the position illustrated in broken lines, but cannot move in the opposite direction past the position ,at which the brace member is straight. With this elbow type of joint, when the brace member 96 is straight it forms a rigid strut member between the connections 84 and 88, and when the brace member is bent as illustrated in broken lines in Fig. 1 it serves to swing the strut I6 rearwardly to move the landing gear from the landing or projected position illustrated in full lines in' Fig. l to the retracted position illustrated in broken lines in which the wheel is positioned within the contour of the wing.v

Owing to the angular elation of the axis of the bearing between the member 12 and the socket 80, the strut is rotated about its own axis as it is swung from its retracted to its extended posiv tion, or vice versa, but when the strut is in its extended position it .is positively-held against rotation by the angular relation between the socket and the strut carrying bearing member and no additional locking device is necessary to restrain the strut against rotation about its own axis.

The landing gear is moved from its projected to its retracted position and vice versa by means particularly illustrated in Fig. 11.

of a screw member generally indicated at II2 and This screw member comprises an externally screw threaded shaft I I4 pivotally connected at its lower end to the pin I08 between the ends of the links I04 and I06 and an internally screw threaded tubular member II6 screw threaded upon the member H4 and hearing at its upper end in a bracket I I8 pivotally secured by means of the integral lugs I20 and pins I22 and I24 to the upper portion of the wing truss. The screw members H4 and H6 are covered by a pair of'telescopically associated tubular members I26 and I28. At its upper end and within the casing II8 the screw member I I6 is provided with a bevel gear I32 which meshes with a beveled gear I34 mounted upon the end of a torque shalt I36, which leads to an operator controlled mechanism by means of which the shaft I36 may be rotated to project or retract the landing gear.

' The operation of the retracting mechanism described above is substantially as follows: Assuming the landing gear wheels to be down as illustrated in full. lines in Fig. 1 and that it is desired to retract the same so that the wheels will lie in the circular openings or pockets I38 provided for them in the undersurface or the wing I0, the shaft I36 will be rotated in a direction to cause the screw-member II4 to screw into the screw member 6, thus shortening the distance between the two ends of the retracting screw I I2.

' pivotally connected to the wing truss at a point positioned above and forwardly of the positions voif the pivotal connection between the brace member 86 and the wing truss, the elbow joint of the brace member 96 will be broken and the pin I08 will be drawn upwardly and forwardly into the wing. This movement of the pin I08 will move the connection 84 rearwardly along an arc centered on the axis of the pin III. This action rotates the innerswivel bearing members 12 in the skewed socket 80 of the outer bearing member undersurface of the wing as illustrated in broken lines at the limiting position of the wheel in Fig.

-1, or in other wordsrotating the plane of the wheel through approximately 90 when the strut is swung approximately 90 to the rear. It is believed that this movement is clearly shown from an inspection of Fig. 1, in which it will be seen that as the strut I6 is swung about the axis of the skewed socket 80 the wheel will travel in an arc tangent to the planes of the wheel in its two limiting positions. It is desired, however, to have the wheel swing straight back from its projected to its retracted position instead of swinging out radially in a direction prescribed by an are centered on the a of the socket 80. In order to accomplish this purpose the pin joint comprising the loop 62 the extension I6 and the pin 16, is provided between the upper end of the strut and the inner member I2 of the swivel bearing and the brace member 96 is made in two laterally spaced parts to support the strut member I6 against loads lateral to the wheel. With this construction as the member 12 rotates in the socket 80, the strut I6 also swings relative to the end of the member I2 so that the wheel moves straight back along an arc in a plane perpendicular to the wing and the strut I6 rotates in the collar 28 as the wheel is marred rearwardly.

The two brace members I04 and I06 may be provided with a diagonal brace member I40 to assist them in taking lateral loads imposed on the wheel the landing gear is attached to the wing it has been found necessary to provide within the wing a strong and rigid truss construction suflicient to carry the heavy loads between the landing gear and the airplane. A suitable wing truss construction is particularly illustrated in Figs. 12 and 13 of the drawings.

In this construction the wing spar or beam I42 comprises an upper and lower member of channel cross section having their flanges interconnected by suitable web members, one of which is indicated in dotted lines at I44. At the point to which the upper end of the brace member 86 is connected to the spar, the web members I44 are cutaway and there is substituted for the web members a pair of rigid brackets I46 disposed between the upper and lower members of the spar. These brackets I46 are each provided with a bearing aperture I48 and are spaced apart so that the bearing openings I48 in the respective brackets I46 receive the ends of the pin 98. Upon each side of the above described I52 attached to the rear surface of the brackets and transverse members and overlying rearwardly entire bearing construction. A pair being reinforced by a web member as indicated at I extending transversely of the front portion of the wing ata position adjacent to the leading edge of the wing. These two heavy ribs I are connected by alongitudinally extending spacer member generally indicated at ill built The link I is hingedly connected at one end' -through the ears and lug up of a plurality of'structural members riveted, welded, or otherwise suitably secured together and-rigidly secured to the'websi" of the ribs -Ill.- 1 The lower portion of the spacer member ill is rnade particularly solid and is provided with an apertured plate I" which overlies the tapered washer ",bolts I82 extending through the flange ll of the bearingbracket .82, the tapered washer 8t and the plate I" flrmly secure the bearing bracket to the specially reinforced internal truss construction of the wing. The portion of the undersurface of the wing between the ribs 54 is cut-away to allow the screw member Ill and the brace to fold up intothe interior of the wing.

4 With the above construction all .vertical loads of the wing are transmitted through the strut ii to the spacer member I" and through this member and the ribs I to the spa'r I42 which is the principal load element carrying the loads between different portions of the wing and the fuselage and between the wings and fuselage and the landing gear. All fore and aft and lateral forces on the wheels are transmitted by the brace member 96 directly to the spar.

In the modified form of the invention illustrated in Figs. 14 and 15, the lower strut member I. is connected to the upper strut member 20 by a pair of'ex'ternal pivoted links i and "6 to restrain the two telescopically associated strut" members against rotation relative to each other.

to a when I which surrounds the lower member I. just below the flange "to which it is rigidly attached by the cap screws 48. The collar III is provided upon one side thereof with an apertured lug and the link'i is provided with a pair of spaced apart apertured ears I10 which overlie the ends of the-lug, a bolt I'll extending pivetally secures the link' to the collar.

The link I85 is similarly pivotally secured to a collar I'll which surrounds the lower end of the upper strut member 2.. The collar I14 is rigidly secured to the strut member by a plu- .rality of set. screws I16 and is provided with an apertured lug I'll, similar to the lug on the collar I", which lies between apertured ears ill formed on the link I.

adjoining ends the links I" and lit are provided with overlapping apertured lug portions ill and I through which extends a bolt I to plvotally secure the two links together. struction the strut member I. is freely slidable in an axial direction with respect to the strut member 2ll, but is restrained against twisting or rotational movement with respect to the member 20 by thev hinged links i and I". The links may be provided in addition to the splines mentioned above, or may .be substituted for the splines and the splines entirely omitted. Also the links may be located at any angular position around the strut so long as they do not inter- A bolt in pivotally secures the link- I to the collar Ill. At their With this confere with the wheel or the retractionof the landing gear and there may be one or a plurality of such linkage devices on each strut, as may be desired or. required by the conditions of a given construction.

From the above description it will be observed that there-has been provided a retractile landing gear in which the wheel moves from a position in a vertical plane transverse to the wing to a 'position in a horizontal plane parallel to the undersurface of the wing and vice versa, and in which the loads in the landing gear are received by a suitable strong and solid truss conthe size, shape, and arrangement of parts may be resorted toas come within the scope of the appended claims, what it is desired to secure by Letters Patent is as follows:

what is claimed is: I 1. In a retractable landing gear, a vertical load strut, a brace for said strut, means operatively connected with said brace for swinging said strut in a substantially vertical are about its point of attachment to the landing gear support from its retractedto its extended position and vice versa, and means comprising a skewed bearing between said strut and said support for rotating said strut in one direction as the strut swings from extended to retracted position and rotating the strut in the opposite direction as the strut swings from retracted to extended position. a

2. In a retractable landing gear, a vertical load strut, a diagonal brace having an intermediate elbow Joint connected at one end to said strut intermediate its length and connected at its other end to the landing gear support, said brace serv-' ing to support said strut against loads other than vertical and'to guide the strut in a straight substantially vertical arc in its swinging movements to or from its extended position from or to its retracted position, means operatively associated with said brace for swinging said strut about its point of attachment to the landing gear supabout its point of attachment to" the landing gear support, and means for pivotally connecting said strut to-said support and rotating said strut during swinging movements thereof comprising, a rotatable bearing between said strut and said sup- I port having its axis of rotation disposed at an oblique angle to the axis of said strut, and a pivotal joint between said strut and said bearing having its axis substantially at right angles to the axis of said strut.

4. In a retractable landing gear, avertical load strut, a brace for said strut, means associated with said brace for extendinhnd retracting said land ing gear, and means for pivotally securing said strut to a landing gear support and rotating said strut during extending and retracting movements of said landing gear, said means comprising, a rotatable bearing including an outer bearing member provided with a socket having its axis disposed at an angle of approximately forty-five degrees downwardly and rearwardly with respect to the axis of said strut, and an inner bearing member rotatable in said socket and attached to the upper end of said strut.

5. In a retractable landing gear supported in an out-board position on the wing of an airplane, a vertical load strut, a brace for said strut, means associated with said brace for extending and retracting said landing gear, and meansvfor pivotally securing said strut to a landing gear support and rotating said strut' during extending and retracting movements of said landing gear, said means comprising, a rotatable bearing including an outer bearing member provided with a socket having its axis disposed at an angle of approximately forty-five degrees downwardly, rearwardly, and inwardly with respect to the axis ofsaid strut, an inner bearing member rotatable in said socket, and a pivotal connection between said inner bearing member and the upper end of said strut.

6. In a retractable landing gear, a vertical load strut, a brace for said strut, means associated with said brace for extending and retracting said landing gear, and means for pivotally securing said strut to a landing gear support and rotating said strut during extending and retracting movements of said landing gear, said means comprising, a rotatable bearing including an outer bearing member provided with a socket having its axis disposedat an obtuse angle to the axis of said strut, an inner bearing member rotatable in said socket, and a pivotal pin connection between the upper end of said strut and said inner bearing member, the axis of said pin being substantially at right angles with the axis of said strut.

'7. In a retractable landing gear, a vertical load strut, a brace for said strut, means associated with said brace for extending and retracting said landing gear, means for pivotally securing said strut to a landing gear support and rotating said strut during extending and retracting movements of said landing gear, said means comprising, a rotatable bearing including an outer bearing member' provided with a socket having its axis disposed at an obtuse angle to the axis-ofsaidstrut, and an inner bearing member rotatable in said socket and a pivotal connection having its axis substantially at right angles to the axis of said strut between said inner bearing member and the upper end of said strut, and cooperating screw threads on the bearing surface of said sockat and said inner bearing member.

8. In a retractable landing gear, a vertical load strut, a bracev for said strut, means associated with said brace for extending and retracting said landing gear, and means for pivotally securing said strut to a landing gear support and rotating said strut during extending and retracting movements or said landing gear, said means comprising, a rotatable bearing including an outer member provided with a socket having its axis disposed at an obtuse angle to the axis of said strut and an inner bearing member rotatable in said socket and attached to the upper end of said strut, a rotatable bearing between said brace and saidstrut and cooperating screw threads between the relatively rotatable elements of said strut bearing and said brace bearing.

9. In an airplane wing having a longitudinal spar comprising an upper member and lower member joined by vertical webs, a retractable landing gear mounting comprising, a pair of' bearing brackets disposed between theupper and lower members of said spar in a cut away portion of said webs and spaced apart in a direction along the longitudinal axis of said wing, a reinforcing structure between the upper and lower members of said spar extending around said bearing brackets to the rear thereof, a cantilever truss extending forwardly from said spar to the leading edge of said wing opposite said bearing brackets and a. mounting plate on the end of said truss adjacent to the leading edge 01' said wing.

10. Invcombination with-an airplane wing having a spar comprising an upper member and a lower member joined together by vertical webs, a. support for a retractable landing gear comprising, a pair of bearing brackets disposed between said upper and lower members of said spar in a cut away portion of said webs, a reinforcing structure between the upper and lower members of said spar extending around said bearing brackets to the rear thereof, a cantilever truss comprising parallel rib members each including flanges and flange connecting webs extending forwardly from said spar, a spacer between said rib members adjacent to the. leading edge of said wing, and a mounting plate on the bottom of said spacer.

KNUT rmmcnsnn. 

